Transcript G050577-00 - DCC

Prospects for the S5 Run
Fred Raab,
LIGO Hanford Observatory
November 8, 2005
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highlights
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Initial LIGO hardware
What have we learned from running S1  S4
Steps to S5; preparing for a long run
Expectations
» Range/duty cycle goals
» Analysis goals
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Issues to study & resolve
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Initial LIGO: Power-recycled
Fabry-Perot-Michelson
suspended mirrors mark
inertial frames
antisymmetric port
carries GW signal
Symmetric port carries
common-mode info
Intrinsically broad band and size-limited by speed of light.
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What Limits Sensitivity
of Interferometers?
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Seismic noise & vibration
limit at low frequencies
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Atomic vibrations (Thermal
Noise) inside components
limit at mid frequencies
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Quantum nature of light
(Shot Noise) limits at high
frequencies
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Myriad details of the lasers,
electronics, etc., can make
problems above these levels
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Some of the technical challenges
for design and commissioning
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Typical Strains < 10-21 at Earth ~ 1 hair’s width at 4 light years
Understand displacement fluctuations of 4-km arms at the
millifermi level (1/1000th of a proton diameter)
Control arm lengths to 10-13 meters RMS
Detect optical phase changes of ~ 10-10 radians
Hold mirror alignments to 10-8 radians
Engineer structures to mitigate recoil from atomic vibrations in
suspended mirrors
Do all of the above 7x24x365
Starting soon at an observatory near you…
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Also: keep tragedy away
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Commissioning and Running Time
Line
1999
2000
2001
2002
2003
2004
2005
2006
3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4
Inauguration First Lock Full Lock all IFO
4K strain noise
Engineering
10-17 10-18
10-20 10-21
E2 E3 E5 E7 E8
Science
Now
S1
E9
S2
10-22
E10
4x10-23
at 150 Hz [Hz-1/2]
E11
S3
S4
S5
Runs
First
Science
Data
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Feedback & Control for Mirrors
and Light
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Damp suspended mirrors to vibration-isolated tables
» 14 mirrors  (pos, pit, yaw, side) = 56 loops
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Damp mirror angles to lab floor using optical levers
» 7 mirrors  (pit, yaw) = 14 loops
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Pre-stabilized laser
» (frequency, intensity, pre-mode-cleaner) = 3 loops
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Cavity length control
» (mode-cleaner, common-mode frequency, common-arm, differential
arm, michelson, power-recycling) = 6 loops
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Wave-front sensing/control
» 7 mirrors  (pit, yaw) = 14 loops
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Beam-centering control
» 3 points  (pit, yaw) = 6 loops
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LIGO Science Runs and what we
learned from them…
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S1: 17 days in Aug-Sep 2002
» 3 LIGO interferometers in coincidence with GEO600 and ~2 days
with TAMA300
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S2: Feb 14 – Apr 14, 2003
» 3 LIGO interferometers in coincidence with TAMA300
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S3: Oct 31, 2003 – Jan 9, 2004
» 3 LIGO interferometers in coincidence with periods of operation of
TAMA300, GEO600 and Allegro
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S4: Feb 22 – Mar 23, 2005
» 3 LIGO interferometers in coincidence with GEO600, Allegro,
Auriga
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After a lot of effort, it works!
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S3 showed we could meet our
RMS goal, but…
Run
S3
L1
21.8%
H1
69.3%
H2
63.4%
Triple
15.8%
Needed to fix the duty cycle
Also wanted to improve highfrequency operation
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Installation of HEPI at Livingston
has improved the stability of L1
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S4 Science Duty Cycle
H1: 80.5%
H2: 81.4%
HEPI delivers!
L1: 74.5%
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TCS system improves recycling cavity
stability, facilitates the use of higher laser power
in the interferometers, better high-frequency
operation
ITM
To ITM HR
surface
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Improvements since S4
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More laser power
Improved oscillator phase noise
Reduced acoustic coupling
Reduction of dust-induced glitches
Reduction of “dewar glitches”
Improved alignment stability
Reduced 60-Hz family of lines in L1
Replaced absorbing H1:ITMX
Improved REFL beam stability
Microseism feedback on H1
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We now think Initial LIGO detector
is ready for a long run
Sensitivity targets*:
Duty Cycle targets:
•H1 inspiral range ~ 10 Mpc
Run
S4
S5
Target
SRD
goal
•L1 inspiral range ~ 10 Mpc
L1
75%
85%
90%
•H2 inspiral range ~ 5 Mpc
H1
81%
85%
90%
H2
81%
85%
90%
3way
57%
70%
75%
* As
measured by SenseMon
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Automated Noise Budget
H1: 11.1 Mpc, Predicted: 15.3, Oct 20 2005 06:43:50 UTC
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DARM
MICH
PRC
Oscillator
OpticalLevers
WFS
OSEM
Seismic
ETM
ITM
BS
SusTherm
IntTherm
Shot
Dark
Intensity
Frequency
Total
SRD
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Displacement [m/ Hz]
10
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10
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10
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10
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10
-20
10
1
10
2
3
10
10
Frequency [Hz]
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Binary Inspiral Search:
LIGO Ranges
binary neutron star range
binary black hole range
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Image: R. Powell
Issues to resolve
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At current sensitivity and duty cycle, it would be a shame not to
start a long run, but some issues remain to be resolved during
the run
Use monitors to identify sources of instrumental transients
Identify low-frequency noise to extend range
Upconversion is known to be important
» Need better vetoes
» Identify and mitigate sources
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Near “the wall” on high power operation
» Protective shutters to handle loss of lock have a tough time
» Steady state AS-port light is stressing photodiodes to limit
» Need to design and implement an output mode cleaner to enable higher
power operation (probably post-S5)
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Low frequency noise not explained
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Displacement noise (m/  Hz)
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H1 noise
H1 predicted
L1 noise
L1 predicted
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Frequency (Hz)
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Possible source:
upconversion from stack motion
Effect measured both at LHO & at LLO:
Using HEPI, increase the suspension point
motion at 1.5 Hz by a factor of 5
DARM noise increases
significantly over a wide band
H1 exhibits a day-to-night variation in low frequency noise, with a ~10%
reduction in inspiral range during the day
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Scattered light fringe wrapping?
BRT
ITM
ETM
Esc~10 -6 E0
For 1% reflection from beam
reducing optics & excitation of
ETMX only
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Stress at the antisymmetric port:
5 msec
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Loss-of-lock: full
beamsplitter power can be
dumped out the AS port, in a
~10 msec width pulse
PD damage due to
~100 W
An example of
photodiode stress
» Too high trigger level
» Shutter failure
» Shutter too slow
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Damaged PDs can be noisy
and position-dependent
Working on shutter
improvements
Steady-state stress
(principally due to AS_I
saturation) needs relief
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Red: replaced
damaged PDs
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What to expect from S5 analyses
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Sensitivity to bursts ~10-21 RMS
Sensitivity to neutron-star inspirals at Virgo cluster
Pulsars
» expect best limits on known neutron star ellipticities at few x10-7
» expect to beat spindown limit on Crab pulsar
» Hierarchical all-sky/all-frequency search
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Cosmic GW background limits expected to be near
GW~10-5
Perhaps a discovery?
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These are exciting times!
Pinning down origins of short
GRBs will result in more solid
estimates of NS-NS and NS-BH
mergers
Groups led by Burrows and Wheeler now have supernova models that
explode! Expect to see action in re-computing GWB waveforms.
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On the more speculative front…
Graphic from KITP
newsletter, heralding an
observable string theory
prediction: GWs from
cosmological strings may be
verified by LIGO in its first
long science run.
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Closing remarks…
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Progressive detector improvements have achieved
design goals
Early implementation of Advanced LIGO techniques
helped achieve goals
» HEPI for duty-cycle boost
» Thermal compensation of mirrors for high-power operation
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Some commissioning breaks expected during S5 to
improve performance and/or reliability
Believe still room for post-S5 improvements
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The Beginning
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